General Pathology: Mechanisms of Disease Explained

Name: General Pathology: Mechanisms of Disease Explained
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Master inflammation, hemodynamics, neoplasia & infection — the universal mechanisms behind every disease you will treat

Role Play

Created byISO Horizon

Last updated 6/2026

English

What you'll learn

Distinguish reversible from irreversible cell injury and identify the patterns of necrosis and regulated cell death
Trace the vascular and cellular events of acute inflammation and the chemical mediators that drive them
Recognize chronic and granulomatous inflammation and explain the mechanisms of tissue repair and wound healing
Apply Virchow's triad to predict thrombosis risk and understand the fates of a thrombus
Classify embolism, infarction, and shock by mechanism, morphology, and clinical stage
Name any tumor correctly using standard nomenclature and distinguish benign from malignant behavior
Explain tumor grading versus staging and apply the TNM system to clinical decision-making
Describe the molecular hallmarks of cancer and the roles of oncogenes, tumor suppressors, and DNA repair genes
Connect chemical, radiation, and viral carcinogens to the specific cancers they cause
Identify the tissue reactions characteristic of each major class of infectious agent

Course content

18 sections • 34 lectures

What Pathology Is and Why It Matters8:20
Pathology is the scientific study of disease, sitting at the bridge between basic science and clinical medicine, and this lecture grounds you in its four classical aspects: etiology (the cause), pathogenesis (the mechanism), morphological changes (what disease looks like in tissues and cells), and clinical manifestations (what the patient experiences). You will learn how general pathology differs from systemic pathology, why understanding disease mechanisms transcends any single organ, and how the same fundamental processes — inflammation, cell death, repair, abnormal growth — recur throughout medicine. Concrete examples illustrate how a pathologist thinks: from a swollen ankle to a tumor biopsy to a sudden cardiac death, each phenomenon traces back to a small set of universal cellular and tissue responses that this course will unpack in depth.
Cellular Adaptations: Hypertrophy, Hyperplasia, Atrophy, Metaplasia8:25
Cells do not passively endure stress — they adapt, and this lecture details the four major reversible adaptations that allow tissues to survive altered demand or environment. You will examine hypertrophy (increased cell size, as in the cardiomyocyte response to hypertension), hyperplasia (increased cell number, such as endometrial proliferation under estrogen), atrophy (shrinkage from disuse, denervation, or hormonal withdrawal), and metaplasia (replacement of one differentiated cell type with another, classically the squamous change in a smoker's bronchus). The lecture explains the molecular signals driving each adaptation, distinguishes physiological from pathological forms, and highlights why metaplasia is a particularly important warning sign — it often marks the soil in which dysplasia and cancer later grow.
Reversible vs Irreversible Cell Injury8:31
When stress exceeds a cell's adaptive capacity, injury begins, and this lecture walks you through the continuum from reversible swelling to the point of no return. You will trace the biochemical cascade triggered by hypoxia — ATP depletion, failure of the sodium pump, cellular swelling, ribosomal detachment, lipid accumulation — and then identify the irreversible landmarks: severe mitochondrial dysfunction, profound membrane damage, and massive calcium influx. The lecture emphasizes morphological correlates visible under the microscope (cytoplasmic eosinophilia, nuclear changes) and clarifies why mitochondrial integrity and membrane stability are the twin gatekeepers determining whether a cell can be saved or is destined to die.
Necrosis: Patterns and Mechanisms8:59
Necrosis is unregulated cell death following severe injury, and its morphological pattern often reveals the underlying cause. This lecture systematically covers coagulative necrosis (the firm, preserved-architecture death of ischemic infarcts in most solid organs), liquefactive necrosis (the soupy destruction seen in brain infarcts and bacterial abscesses), caseous necrosis (the cheesy hallmark of tuberculosis), fat necrosis (saponification in acute pancreatitis), fibrinoid necrosis (a vascular wall pattern in immune injury), and gangrenous necrosis (the clinical term for limb ischemia with or without superimposed infection). You will learn to connect each morphology to its typical etiology and anatomical location, building the pattern recognition that pathologists use every day.
Apoptosis and Other Regulated Cell Death13:36
Apoptosis is programmed, energy-dependent cell suicide that disposes of unwanted cells without inflammation, and this lecture explores its intrinsic (mitochondrial) and extrinsic (death receptor) pathways, the role of the caspase cascade, and the morphological hallmarks of cell shrinkage, chromatin condensation, and apoptotic body formation. You will see how apoptosis serves physiological roles — embryogenesis, immune selection, cyclic endometrial shedding — and pathological ones, from viral infection clearance to the unwanted neuronal loss of neurodegeneration. The lecture also introduces newer regulated death modes such as necroptosis, pyroptosis, and ferroptosis, explaining how each fits into modern understanding of inflammation, infection, and tissue damage.
Intracellular Accumulations and Pathologic Calcification10:05
Injured or metabolically deranged cells often accumulate abnormal substances, and this lecture surveys the major patterns: fatty change in the liver from alcohol or obesity, cholesterol deposits in atherosclerotic plaques and xanthomas, protein accumulations in conditions such as alpha-1-antitrypsin deficiency, glycogen storage in diabetes and inherited enzyme defects, and pigment deposition including lipofuscin, melanin, and hemosiderin. You will then explore pathologic calcification in its two forms — dystrophic, which occurs in dying or dead tissue despite normal serum calcium, and metastatic, which deposits in normal tissue when calcium-phosphate homeostasis fails. Concrete clinical examples anchor each accumulation to a disease you will recognize.
Section 1 Quiz: Foundations of Disease: Cell Injury and Adaptation
Roleplay: Foundations of Disease: Cell Injury and Adaptation

Acute Inflammation: Vascular Events8:33
Acute inflammation is the body's rapid, stereotyped response to injury, and its vascular phase produces the classical clinical signs of redness, heat, and swelling. This lecture details the sequence of momentary vasoconstriction followed by sustained vasodilation, the increase in vascular permeability through endothelial contraction and direct injury, and the resulting exudation of protein-rich fluid into tissues. You will learn how stasis develops as blood flow slows and red cells concentrate, setting the stage for leukocyte margination. Crisp definitions of exudate versus transudate, along with vivid examples like a sunburned arm or an infected finger, anchor the abstract physiology in everyday experience.
Acute Inflammation: Cellular Events and Leukocyte Recruitment9:15
Inflammation's cellular phase delivers neutrophils to the site of injury through a precisely choreographed sequence, and this lecture walks you through each step: margination as cells drift to the vessel wall, rolling on selectins, firm adhesion via integrins binding ICAM and VCAM, transmigration through endothelial junctions, and chemotaxis along gradients of bacterial peptides, complement fragments, and chemokines. You will then explore phagocytosis itself — recognition through opsonins like IgG and C3b, engulfment, phagolysosome formation, and microbial killing by oxygen-dependent and oxygen-independent mechanisms. The defects in leukocyte adhesion deficiency and chronic granulomatous disease illustrate what happens when this machinery fails.
Chemical Mediators of Inflammation11:32
Inflammation is orchestrated by a rich cast of chemical mediators, and this lecture organizes them into a clear framework you can actually remember. You will study vasoactive amines (histamine and serotonin), arachidonic acid metabolites (prostaglandins, leukotrienes, lipoxins) and the pharmacology that targets them with NSAIDs and steroids, platelet-activating factor, cytokines such as TNF and IL-1 with their fever and acute phase responses, chemokines that guide leukocyte traffic, complement components (C3a, C5a, the membrane attack complex), the kinin system that generates bradykinin, and reactive oxygen species and nitric oxide. Each mediator is paired with its source, action, and a clinical drug or disease that makes it stick.
Outcomes of Acute Inflammation9:03
Acute inflammation does not last forever — it resolves into one of several outcomes, and this lecture details each trajectory. Complete resolution restores normal tissue when injury is mild and the parenchyma can regenerate. Healing by connective tissue replacement (scarring) follows substantial tissue destruction or when the injured tissue cannot regenerate. Abscess formation occurs with pyogenic bacterial infections, producing localized collections of pus. Progression to chronic inflammation happens when the offending agent persists. You will also encounter the morphologic patterns of acute inflammation — serous, fibrinous, purulent, and ulcerative — each with characteristic settings such as blister fluid, pericarditis, appendicitis, and peptic ulcer disease.
Chronic Inflammation: Causes and Cellular Players8:17
Chronic inflammation persists for weeks, months, or years and is characterized by ongoing inflammation, tissue injury, and attempts at repair occurring simultaneously. This lecture identifies its three main triggers: persistent infections by hard-to-eradicate organisms like Mycobacterium tuberculosis and Treponema pallidum, prolonged exposure to toxic agents such as silica or atherogenic lipids, and autoimmune diseases like rheumatoid arthritis. You will study the dominant cellular cast — macrophages with their M1 and M2 polarization, lymphocytes engaging in adaptive immunity, plasma cells producing antibodies, eosinophils in parasitic and allergic disease, and mast cells — and learn how their crosstalk sustains the smoldering tissue damage that defines chronic disease.
Granulomatous Inflammation10:10
Granulomatous inflammation is a distinctive pattern of chronic inflammation defined by collections of activated macrophages transformed into epithelioid cells, often fused into multinucleated giant cells and surrounded by lymphocytes. This lecture distinguishes caseating granulomas (the necrotic-centered hallmark of tuberculosis) from non-caseating granulomas (seen in sarcoidosis, Crohn disease, foreign body reactions, and cat scratch disease). You will examine the immunologic mechanism — Th1-driven cytokine signaling, particularly interferon-gamma — that organizes a granuloma, and learn why this pattern represents both a triumph of containment and a chronic problem when the inciting agent cannot be cleared.
Tissue Repair: Regeneration and Scar Formation7:21
Tissue repair restores structure after injury, and this lecture distinguishes the two fundamental strategies the body uses. Regeneration replaces damaged cells with cells of the same type and works only when stable or labile tissues are involved and the underlying scaffold is intact — examples include liver regeneration after partial hepatectomy and epidermal renewal after a superficial abrasion. Scar formation by connective tissue deposition takes over when injury is severe, when permanent tissues like cardiac muscle and neurons are damaged, or when the extracellular matrix scaffold is destroyed. You will learn the roles of growth factors such as EGF, PDGF, VEGF, and TGF-beta, and the central importance of the fibroblast and the macrophage.
Wound Healing and Factors That Affect It7:36
Cutaneous wound healing illustrates repair in action, and this lecture details its overlapping phases: hemostasis and inflammation in the first minutes to days, proliferation with formation of granulation tissue (new capillaries, fibroblasts, loose collagen) over the following week, and remodeling that may continue for months as type III collagen is replaced by stronger type I and tensile strength gradually recovers. You will contrast healing by first intention (a clean surgical incision) with healing by second intention (a large, gaping wound) and learn the systemic factors (nutrition, diabetes, glucocorticoids, age) and local factors (infection, foreign bodies, poor perfusion) that derail healing, producing complications like dehiscence, keloids, hypertrophic scars, and contractures.
Section 2 Quiz: Inflammation and Tissue Repair
Roleplay: Inflammation and Tissue Repair

Edema: Mechanisms and Clinical Patterns8:43
Edema is the accumulation of fluid in the interstitium or body cavities, and this lecture frames it through the Starling forces that govern fluid movement across capillary walls. You will examine the major pathophysiologic categories: increased hydrostatic pressure (heart failure causing dependent edema, deep vein thrombosis causing limb swelling), decreased plasma oncotic pressure (nephrotic syndrome, cirrhosis, malnutrition), lymphatic obstruction (filariasis, post-mastectomy arm swelling), sodium and water retention (renal disease), and inflammation. Distinguishing transudate from exudate by protein content and specific gravity, and recognizing pulmonary edema, ascites, hydrothorax, and anasarca, gives you a clinical vocabulary you will use throughout medicine.
Hyperemia, Congestion, and Hemorrhage6:47
Hyperemia is an active process of increased blood inflow producing the red, warm tissue of exercise or inflammation, while congestion is the passive accumulation of venous blood — slower, bluer, and often pathologic. This lecture details the morphologic consequences of chronic passive congestion, including nutmeg liver from right heart failure and brown induration of the lung from left heart failure with hemosiderin-laden heart failure cells. You will then turn to hemorrhage, defined as the escape of blood from the vascular compartment, surveying the spectrum from petechiae and purpura to ecchymoses and large hematomas, and the clinical consequences that depend on volume lost, rate of loss, and location (intracranial bleeding being especially dangerous in confined spaces).
Hemostasis and the Normal Clotting Sequence10:01
Before disease can derail clotting, you must understand the normal hemostatic response, and this lecture walks through its three integrated steps. Primary hemostasis is the platelet response: adhesion to exposed collagen via von Willebrand factor, activation, granule release, and aggregation through GpIIb/IIIa receptors binding fibrinogen. Secondary hemostasis activates the coagulation cascade — intrinsic and extrinsic pathways converging on factor X to generate thrombin, which converts fibrinogen to fibrin and stabilizes the platelet plug. Finally, counter-regulatory mechanisms (antithrombin, protein C and S, tissue factor pathway inhibitor) and fibrinolysis (plasminogen to plasmin) ensure clots stay localized and eventually dissolve.
Thrombosis and Virchow's Triad8:00
Thrombosis is inappropriate clot formation within an intact vessel, and Virchow's triad provides the timeless framework for understanding why it happens. This lecture details endothelial injury (the dominant factor in arterial thrombosis, as in atherosclerosis and myocardial infarction), abnormal blood flow including stasis (favoring venous thrombosis in bedridden patients) and turbulence (in aneurysms and at arterial bifurcations), and hypercoagulability — both inherited (factor V Leiden, prothrombin gene mutation, protein C and S deficiency) and acquired (malignancy, oral contraceptives, antiphospholipid syndrome, nephrotic syndrome). You will examine the morphology of arterial versus venous thrombi, with attention to the lines of Zahn that mark a true antemortem thrombus, and learn the four possible fates of a thrombus: propagation, embolization, dissolution, and organization with or without recanalization.
Embolism: Pulmonary, Systemic, and Special Types8:56
An embolus is a detached intravascular solid, liquid, or gaseous mass carried by the blood to a site distant from its origin, and most arise from dislodged thrombi. This lecture covers pulmonary embolism arising from deep vein thrombosis of the lower extremities, with its spectrum from clinically silent small emboli to massive saddle emboli causing sudden death. Systemic embolism most often originates in the left heart from mural thrombi after myocardial infarction or in atrial fibrillation, lodging in the brain, kidneys, spleen, or lower limbs. You will then encounter the specialized embolic syndromes: fat embolism after long bone fracture, air embolism from decompression sickness or vascular procedures, and amniotic fluid embolism, a rare but devastating complication of labor with high maternal mortality.
Infarction: Red vs White and the Factors That Decide11:35
Infarction is an area of ischemic necrosis caused by occlusion of either the arterial supply or venous drainage to a tissue, and this lecture explains why infarcts come in two colors. White (pale) infarcts develop in solid organs with end-arterial circulation like the heart, spleen, and kidney, where arterial occlusion produces wedge-shaped coagulative necrosis with little secondary hemorrhage. Red (hemorrhagic) infarcts occur with venous occlusion (testicular torsion), in loose tissues that allow blood to seep in (lung), in tissues with dual circulation (lung, small intestine), and when previously infarcted tissue is reperfused. You will examine the factors that determine whether and how severely tissue infarcts: nature of the vascular supply, rate of occlusion, tissue vulnerability to hypoxia (neurons most sensitive, fibroblasts most resistant), and oxygen content of the blood.
Shock: Types, Pathogenesis, and Stages10:34
Shock is a state of systemic hypoperfusion that causes cellular hypoxia, and this lecture organizes its five major types around mechanism. Cardiogenic shock results from pump failure (massive myocardial infarction, arrhythmia, tamponade). Hypovolemic shock follows loss of blood or plasma volume (hemorrhage, burns, severe diarrhea). Septic shock arises from systemic inflammation triggered by infection, with widespread vasodilation, endothelial injury, and disseminated intravascular coagulation driven by cytokine storm. Anaphylactic shock is a systemic type I hypersensitivity reaction with mast cell degranulation. Neurogenic shock follows loss of vascular tone after spinal injury. You will then trace the three clinical stages — nonprogressive (compensated), progressive, and irreversible — and understand why early recognition is everything.
Section 3 Quiz: Hemodynamic Disorders: Fluid, Bleeding, and Thrombosis
Roleplay: Hemodynamic Disorders: Fluid, Bleeding, and Thrombosis

Nomenclature and Classification of Tumors11:22
Tumor nomenclature follows a logical system, and once you grasp the rules you can decode any tumor name you encounter. This lecture explains how benign tumors of mesenchymal origin take the suffix -oma (lipoma, leiomyoma, osteoma), while malignant mesenchymal tumors are called sarcomas (liposarcoma, leiomyosarcoma, osteosarcoma). Benign epithelial tumors carry varied names — adenoma for glandular patterns, papilloma for finger-like projections, cystadenoma for cystic lesions — while malignant epithelial tumors are carcinomas, further subdivided into adenocarcinoma and squamous cell carcinoma. You will also meet important exceptions whose names mislead — lymphoma, melanoma, seminoma, and glioma are all malignant despite the -oma suffix — and learn about mixed tumors, teratomas, hamartomas, and choristomas.
Benign vs Malignant: Six Defining Differences10:25
The distinction between benign and malignant neoplasms rests on a constellation of features, and this lecture lays them out systematically. You will compare differentiation and anaplasia (benign tumors closely resemble their tissue of origin while malignant ones often show pleomorphism, abnormal nuclei, and loss of polarity), rate of growth (generally slow versus rapid with high mitotic activity), local invasion (encapsulation versus infiltrative destruction), and metastasis (the single most reliable malignant feature). You will also examine functional characteristics, the practical consequences for the patient, and the gray zones where intermediate behavior — locally aggressive but non-metastasizing tumors like basal cell carcinoma — challenges any rigid dichotomy.
Tumor Grading and Staging8:03
Grading and staging are two complementary ways of describing a malignant tumor, and confusing them is a classic novice error this lecture will prevent. Grading is a histologic assessment of how differentiated tumor cells are, typically reported on a scale from well-differentiated (grade 1) to undifferentiated or anaplastic (grade 3 or 4), based on mitotic count, nuclear features, and architectural patterns. Staging describes the anatomic extent of disease using the TNM system: T for tumor size and local extent, N for regional lymph node involvement, and M for distant metastasis. You will learn why staging generally has greater clinical impact on treatment and prognosis than grading, and how both work together to guide therapy.
The Molecular Hallmarks of Cancer10:26
Cancer arises from accumulated genetic alterations that confer a set of acquired capabilities, and this lecture builds on the celebrated hallmarks framework to organize your understanding. You will study self-sufficiency in growth signals through activated oncogenes, insensitivity to growth-inhibitory signals through loss of tumor suppressors, evasion of apoptosis, limitless replicative potential through telomerase reactivation, sustained angiogenesis driven by VEGF, and the capacity for invasion and metastasis. Newer hallmarks — reprogrammed energy metabolism (the Warburg effect) and evasion of immune destruction — round out the framework. The lecture grounds each capability in specific gene examples so the abstraction becomes concrete.
Oncogenes, Tumor Suppressors, and DNA Repair Genes11:23
Three classes of genes underlie cancer, and this lecture details each with canonical examples. Proto-oncogenes encode proteins that promote growth (growth factors, receptors, signal transducers, transcription factors, cell-cycle regulators) and become oncogenes when activated by point mutation, amplification, or translocation — think RAS in colon cancer, MYC in Burkitt lymphoma, HER2 in breast cancer, and BCR-ABL in chronic myeloid leukemia. Tumor suppressor genes normally restrain growth and require loss of both alleles to fail, as Knudson's two-hit hypothesis explains for RB in retinoblastoma; TP53 stands as the most frequently mutated gene in human cancer. DNA repair genes maintain genomic stability — defects in BRCA1 and BRCA2 predispose to breast and ovarian cancer, while mismatch repair defects underlie Lynch syndrome.
Carcinogenesis: Chemical, Radiation, and Viral Causes10:55
Cancer is caused by environmental and infectious agents that damage DNA, and this lecture surveys the three major categories with vivid clinical pairings. Chemical carcinogens include direct-acting agents and indirect-acting procarcinogens requiring metabolic activation — polycyclic aromatic hydrocarbons in tobacco smoke causing lung cancer, aflatoxin from Aspergillus contaminating grain causing hepatocellular carcinoma, aromatic amines causing bladder cancer, and vinyl chloride causing angiosarcoma of the liver. Radiation carcinogenesis covers ultraviolet light (skin cancers), ionizing radiation (leukemia and thyroid cancer after atomic blasts and Chernobyl), and the multi-hit model. Viral oncogenesis includes HPV in cervical cancer, hepatitis B and C in hepatocellular carcinoma, Epstein-Barr virus in Burkitt and nasopharyngeal cancers, HHV-8 in Kaposi sarcoma, HTLV-1 in adult T-cell leukemia, and H. pylori as a bacterial example causing gastric carcinoma and MALT lymphoma.
Tumor Immunity and Immune Evasion10:55
The immune system continuously surveys for transformed cells, and this lecture explains both how it recognizes them and how cancers escape. You will study tumor antigens — products of mutated genes, overexpressed normal proteins, oncoviral proteins, and cancer-testis antigens — and the immune effectors that target them: cytotoxic T lymphocytes recognizing peptide-MHC complexes, NK cells targeting cells with downregulated MHC, and macrophages and antibodies contributing through ADCC. Tumors evade immunity by losing MHC expression, secreting immunosuppressive cytokines like TGF-beta, recruiting regulatory T cells, and expressing checkpoint ligands such as PD-L1. This biology explains why checkpoint inhibitor immunotherapy has revolutionized oncology over the past decade.
Clinical Features of Cancer: Local Effects, Paraneoplastic Syndromes, and Cachexia10:23
Tumors harm patients through several pathways, and this lecture organizes those effects so you can recognize them clinically. Local effects include mass compression of adjacent structures, obstruction of hollow viscera, ulceration with bleeding, and infection. Hormonal effects arise from functional endocrine tumors. Paraneoplastic syndromes are remote effects unexplained by the tumor's local spread or its hormone of origin — Cushing syndrome from ectopic ACTH in small cell lung cancer, SIADH, hypercalcemia from PTHrP in squamous cell carcinoma, and an array of neurologic, dermatologic, and hematologic syndromes. Cancer cachexia is a wasting syndrome driven by cytokines such as TNF and IL-6 that produces weight loss disproportionate to caloric intake and contributes substantially to mortality.
Section 4 Quiz: Neoplasia: Biology and Behavior of Tumors
Roleplay: Neoplasia: Biology and Behavior of Tumors

Categories of Infectious Agents9:17
Infectious agents span a vast biological range, and this lecture organizes them into the categories you must know. Viruses are obligate intracellular agents with DNA or RNA genomes, exemplified by influenza, HIV, hepatitis, and herpesviruses. Bacteria include gram-positive cocci like Staphylococcus and Streptococcus, gram-negative rods like E. coli and Pseudomonas, mycobacteria with their waxy walls, and spirochetes like Treponema. Fungi range from yeasts like Candida to molds like Aspergillus and dimorphic fungi. Parasites include protozoa (Plasmodium, Entamoeba, Toxoplasma) and helminths (nematodes, trematodes, cestodes). Prions, the unique protein-only agents, cause diseases such as Creutzfeldt-Jakob. Each category demands a different diagnostic approach and provokes a characteristic tissue reaction.
How Microorganisms Cause Disease8:33
Microorganisms harm the host through a definable set of mechanisms, and this lecture details each. Direct cytopathic effects include viral lysis of infected cells, bacterial production of cytolytic toxins, and parasitic destruction of red blood cells in malaria. Toxin-mediated disease ranges from the preformed toxins of botulism and staphylococcal food poisoning to the secreted exotoxins of cholera and diphtheria, and the endotoxin (lipopolysaccharide) of gram-negative bacteria that triggers septic shock. Immune-mediated injury occurs when the host response itself causes damage, as in the granulomatous destruction of tuberculosis or the immune complex glomerulonephritis after streptococcal infection. Some organisms induce cellular proliferation that becomes neoplastic, linking infection to cancer.
Host-Pathogen Interactions and Routes of Entry11:11
Disease results from a contest between microbial virulence and host defense, and this lecture frames that interaction. You will explore portals of entry — skin (typically requires a breach), respiratory tract (the most common route), gastrointestinal tract (acid and bile as barriers, fecal-oral transmission), urogenital tract, and direct inoculation through bites or needles. Mechanisms of spread include local extension, lymphatic dissemination to regional nodes, hematogenous spread producing bacteremia, viremia, or sepsis, and transplacental transmission. Host defenses include physical and chemical barriers, the innate immune response (complement, phagocytes, NK cells), and the adaptive immune response with its specific antibodies and T cells. Immunodeficiency — whether congenital, iatrogenic, or from HIV — tips this balance toward the pathogen.
Tissue Reactions to Infection8:04
The tissue response to infection often reveals the responsible class of organism, and this pattern recognition is the pathologist's daily tool. Suppurative (purulent) inflammation with neutrophilic infiltrates is the hallmark of pyogenic bacteria like Staphylococcus and Streptococcus, producing abscesses. Mononuclear and granulomatous inflammation with lymphocytes, macrophages, and giant cells suggests intracellular bacteria like Mycobacterium tuberculosis or fungi like Histoplasma. Cytopathic-cytoproliferative reactions with viral inclusion bodies and giant cells characterize many viral infections — Cowdry bodies of herpes, the owl-eye inclusions of cytomegalovirus, the Negri bodies of rabies. Necrotizing inflammation occurs with highly virulent organisms, while chronic inflammation with scarring follows persistent infection.
Emerging Infections and Antimicrobial Resistance11:07
Infectious disease pathology is not static, and this lecture closes the course by examining the dynamic forces shaping modern infection. Emerging infections arise through ecological change, animal-human contact, global travel, and microbial evolution — HIV, SARS, Ebola, Zika, and the coronavirus pandemics all illustrate how new pathogens reach human populations. Re-emerging infections like tuberculosis and measles reflect failures of public health and vaccination. Antimicrobial resistance, driven by overuse and misuse of antibiotics in medicine and agriculture, has produced organisms like MRSA, VRE, ESBL-producing gram-negatives, carbapenem-resistant Enterobacteriaceae, and multidrug-resistant tuberculosis. You will appreciate why understanding pathology equips you to interpret these threats and contribute to managing them.
Section 5 Quiz: Infectious Disease Pathology
Roleplay: Infectious Disease Pathology

Requirements

Basic understanding of human cell biology and biochemistry
Familiarity with fundamental human anatomy and organ systems
Working knowledge of introductory physiology, especially circulation and immunity
Interest in medicine, dentistry, or an allied health discipline

Description

This course contains the use of artificial intelligence.

Every disease you will ever encounter — whether a swollen joint, a heart attack, a tumor on a scan, or a deadly infection — traces back to a small set of universal mechanisms that pathology has spent two centuries decoding. General pathology is the conceptual foundation of all clinical medicine, and without it organ-specific knowledge becomes a list of facts to memorize rather than a coherent science to understand. This course gives you that foundation in a structured, vivid, and clinically grounded way.

You will begin with cell injury and adaptation, learning how cells respond to stress, when adaptation tips into reversible injury, and what defines the point of no return that commits a cell to necrosis or apoptosis. You will then master inflammation in depth — the vascular and cellular events of the acute response, the rich chemistry of mediators, the cellular cast of chronic inflammation, the distinctive pattern of granulomatous disease, and the orchestrated phases of tissue repair and wound healing. Hemodynamic disorders come next, with thorough coverage of edema, congestion, hemorrhage, thrombosis and Virchow's triad, every major type of embolism, the difference between red and white infarcts, and the five categories of shock with their pathogenesis and clinical stages. The neoplasia section builds a complete framework for understanding cancer: tumor nomenclature, the features distinguishing benign from malignant growth, grading and staging, the molecular hallmarks of cancer, oncogenes and tumor suppressors and DNA repair genes, chemical and radiation and viral carcinogenesis, tumor immunity, and the clinical syndromes that cancer produces including paraneoplastic effects and cachexia. The course closes with infectious disease pathology, examining how microorganisms cause disease, how host-pathogen interactions determine outcomes, and the characteristic tissue reactions that point to each class of agent.

This course is designed for medical and dental students preparing for board examinations, pathology residents building their conceptual foundation, allied health professionals who need to understand disease mechanisms at a deeper level, and any motivated learner who wants to make sense of how the body breaks down and how it tries to repair itself. No prior pathology background is required, only a working knowledge of basic biology and human anatomy. By the end you will think the way pathologists think — recognizing patterns, reasoning from mechanism to morphology to clinical presentation, and connecting the dots across every organ system you will later study.

What sets this course apart is its commitment to teaching pathology as a way of thinking rather than a body of facts to memorize. Every concept is grounded in concrete clinical examples, every mechanism is paired with the disease it explains, and every section builds on the last to give you a lasting framework. Enroll now and gain the conceptual foundation that will serve you for the rest of your medical career.

Who this course is for:

Medical students preparing for pathology coursework or board examinations
Dental students studying general pathology as part of their curriculum
Pathology residents reviewing core concepts and building a teaching framework
Nursing, pharmacy, and allied health students who need a working understanding of disease mechanisms
Motivated learners and pre-health students curious about how diseases actually develop

General Pathology: Mechanisms of Disease Explained

What you'll learn

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Course content

Section 1: Foundations of Disease: Cell Injury and Adaptation7 lectures • 58min

Section 2: Inflammation and Tissue Repair9 lectures • 1hr 12min

Section 3: Hemodynamic Disorders: Fluid, Bleeding, and Thrombosis8 lectures • 1hr 5min

Section 4: Neoplasia: Biology and Behavior of Tumors9 lectures • 1hr 24min

Section 5: Infectious Disease Pathology6 lectures • 48min

Introduction to Pathology and Cellular Injury0

Cell Death and Tissue Response0

Acute Inflammation and Immune Responses0

Chronic Inflammation and Healing0

Hemodynamic Disorders and Thrombosis0

Requirements

Description

Who this course is for: